A lead-free double perovskite luminescent material, and a preparation method and application thereof

Abstract

This invention discloses a lead-free double perovskite luminescent material, its preparation method, and its applications. This material exhibits excellent downconversion luminescence performance and thermal stability. The preparation method provided by this invention is a solvothermal method: raw materials CsCl, NaCl, and LuCl3•6H2O are placed in a polytetrafluoroethylene (PTFE) liner; YbCl3•6H2O, K2ReCl6, and CsF are added, and 10 ml of hydrochloric acid is injected as a solvent. The mixture is stirred for 1 hour to ensure thorough mixing; finally, the PTFE liner is placed in a reaction vessel liner, and the reaction is carried out in an oven. After the reaction, the mixture is slowly cooled to room temperature in the oven, cleaned with anhydrous ethanol, and dried to obtain the lead-free double perovskite material. The lead-free double perovskite material exhibits near-infrared luminescence with high quantum yield at approximately 1355 nm under 980 nm excitation. It can be used as a fluorescence conversion layer for marking and illumination in infrared LED light sources or infrared imaging systems, and is suitable for fields such as medical diagnosis and industrial inspection.

Description

Technical Field

[0001] This invention relates to the field of lead-free double perovskite luminescent materials, specifically to a lead-free double perovskite luminescent material, its preparation method, and its application. Background Technology

[0002] Lead halide perovskites have been widely studied and applied in solid-state lighting, photodetectors, solar cells, and anti-counterfeiting, but their poor stability and high toxicity limit their practical applications. To address this, an environmentally friendly lead-free double perovskite material, A2MMʹCl6 (A = Cs, Rb, K; M = Na, Ag, Li; Mʹ = Yb, In, Bi, etc.), has been developed. This type of vacancy-ordered structure endows it with excellent photoelectric properties such as strong absorption, long carrier diffusion distance, and broadband emission from the visible to near-infrared range, offering high design freedom in luminescence modulation and bandgap engineering. Taking Cs2NaLuCl6 as an example, it possesses advantages such as being lead-free, low-toxicity, and having mild synthesis conditions, but still suffers from problems such as a narrow excitation wavelength range and insufficient near-infrared luminescence intensity.

[0003] Meanwhile, developing broadband near-infrared phosphors with emission peaks exceeding 1300 nm is of great significance for expanding the applications of near-infrared light sources. While existing systems based on Cr³⁺ and Ni²⁺ have achieved correlated luminescence, they generally suffer from low internal quantum efficiency, weak absorption efficiency, and poor thermal stability. The luminescence of single-doped systems is also strongly constrained by the crystal field. Therefore, there is an urgent need to develop novel near-infrared luminescent centers. Re phosphors with a 5d³ configuration... 4 ⁺ Due to its strong spin-orbit coupling (SOC), it can relax the spin selection rule, improve near-infrared quantum efficiency, and can be transmitted via Yb³⁺→Re 4 - Energy transfer enables broadband near-infrared emission excited at 980 nm, demonstrating promising application potential. Previous studies have reported on Re... 4 While Cs₂ZrCl₆ exhibits visible and near-infrared luminescence properties, achieving high quantum efficiency in dual perovskite near-infrared luminescent materials remains challenging.

[0004] Therefore, the present invention provides a lead-free double perovskite luminescent material, its preparation method, and its application. Summary of the Invention

[0005] The purpose of this invention is to provide a lead-free double perovskite luminescent material, its preparation method, and its application, so as to solve the problems existing in the above-mentioned background art.

[0006] To achieve the above-mentioned technical effects, the present invention is implemented through the following technical solution: a lead-free double perovskite luminescent material, wherein the lead-free double perovskite luminescent material is based on Cs2NaLuCl6 as a double perovskite matrix and doped with Yb. 3+ Re 4+ F - .

[0007] The present invention also provides a method for preparing the lead-free double perovskite luminescent material as described above, comprising the following steps:

[0008] S1: Add CsCl, NaCl, and LuCl3•6H2O to the polytetrafluoroethylene liner and mix to obtain mixture A;

[0009] S2: Add YbCl3•6H2O, K2ReCl6, CsF and hydrochloric acid to mixture A, stir thoroughly, and mix evenly to obtain mixture B;

[0010] S3: Place mixture B in an oven for reaction, cool to room temperature, wash and dry with anhydrous ethanol to obtain a near-infrared luminescent lead-free double perovskite luminescent material.

[0011] Furthermore, in S1, the molar ratio of CsCl, NaCl, and LuCl3•6H2O is CsCl:NaCl:LuCl3•6H2O = 2:1:1.

[0012] Furthermore, in S2, YbCl3·6H2O and K2ReCl6 serve as the Yb³⁺ source and Re source, respectively. 4 The F⁺ source was added, wherein the amount of YbCl3·6H2O added was 20% of the amount of LuCl3·6H2O, and the amount of K2ReCl6 added was 1% of the amount of LuCl3·6H2O; CsF was added as an F⁻ source, and the amount of CsF added was 6% of the total amount of Cl⁻.

[0013] Furthermore, in step S3, the reaction conditions of the mixture B in the oven are 180°C for 12 hours.

[0014] In addition, the present invention also provides the application of the lead-free double perovskite luminescent material as described above in LED imaging.

[0015] The beneficial effects of this invention are:

[0016] The lead-free double perovskite luminescent material prepared by the method of the present invention exhibits excellent thermal stability, achieving near-zero thermal quenching, and retaining approximately 95% of its luminescence intensity at 423 K. Simultaneously, Yb³⁺ and Re are synergistically introduced into the [LuCl6]³⁻ octahedral lattice of Cs₂NaLuCl₆. 4 ⁺, and partially replace Cl⁻ with F⁻, using the size difference of different ions to control the lattice parameters, making the crystal structure more stable and ordered;

[0017] By introducing Yb³⁺ as a sensitizer for 980nm excitation into a Cs₂NaLuCl₆ matrix and co-doping with Re… 4 Using F⁻ as the luminescent center and partially replacing Cl⁻ with F⁻ to modulate the local crystal field environment, this strategy significantly enhances the thermal stability of the material in the near-infrared band.

[0018] The ordered double perovskite matrix Cs₂NaLuCl₆ selected in this invention possesses excellent structural stability and low phonon energy, which is beneficial for reducing nonradiative relaxation losses; Yb³⁺ and Re 4 Co-doping between ⁺ and ⁺ can effectively improve the Yb³⁺-to-Re conversion. 4 The high transmission efficiency of F⁺ results in high-intensity near-infrared emission around 1355 nm under excitation at approximately 980 nm. Furthermore, the introduction of F⁻ further optimizes the octahedral coordination symmetry and enhances the luminescence transition probability. In addition, the lead-free double perovskite luminescent material obtained in this invention can be used as a near-infrared fluorescence conversion material for LED imaging. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 In Example 2, Cs2NaLuCl6:20%Yb 3+ / 1%Re / 6%F - Crystal structure diagram of lead-free double perovskite material; Figure 2 The images show the X-ray diffraction (XRD) data of the Cs2NaLuCl6 lead-free double perovskite materials in Examples 1 and 2. Figure 3 The image shows the scanning electron microscope (SEM) morphology of the Cs2NaLuCl6 lead-free double perovskite material in Example 2. Figure 4 The graph shows a comparison of the emission intensity of the Cs2NaLuCl6 lead-free double perovskite materials in Examples 1 and 2 under 980 nm excitation. Figure 5 The graph shows a comparison of the temperature-dependent emission intensity of the Cs2NaLuCl6 lead-free double perovskite material under 980 nm excitation versus its room temperature emission intensity in Examples 1 and 2. Figure 6 Yb in Example 3 3+ 1%Re 4+ Emission spectra of lead-free double perovskite materials at various concentrations; Figure 7 Re in Example 4 4+ 20% Yb 3+ Emission spectra of lead-free double perovskite materials at various concentrations; Figure 8 For example, F in Example 5 - 1%Re 4+ 20% Yb 3+ Emission spectra of lead-free double perovskite materials at various concentrations; Figure 9 20% Yb in Example 1 3+ 1%Re 4+ Near-infrared quantum efficiency of a double-doped lead-free perovskite material under 980 nm excitation; Figure 10 20% Yb in Example 2 3+ 1%Re 4+ Near-infrared quantum efficiency of 6%F⁻ triple-doped lead-free double perovskite material under 980nm excitation; Figure 11 20% Yb in Example 2 3+ 1%Re 4+ Physical image and imaging effect of 6%F⁻ triple-doped lead-free double perovskite material under 980nm LED chip power-on conditions. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] This embodiment provides a Yb 3+ Re 4+A method for preparing a lead-free double-doped Cs₂NaLuCl₆ perovskite luminescent material, wherein the molar ratio of CsCl, NaCl, and LuCl₃•₆H₂O is CsCl:NaCl:LuCl₃•₆H₂O = 2:1:1, the amount of YbCl₃•₆H₂O added is 20% of the amount of LuCl₃•₆H₂O, and the amount of K₂ReCl₆ added is 1% of the amount of LuCl₃•₆H₂O. The specific preparation steps are as follows:

[0034] (1) CsCl, NaCl, and LuCl3•6H2O were added to the polytetrafluoroethylene liner according to the proportion to obtain mixture A;

[0035] (2) Next, add YbCl3•6H2O, K2ReCl6 and hydrochloric acid to the mixture A in step (1) and stir thoroughly to obtain mixture B;

[0036] (3) Finally, the mixture B obtained in step (2) was placed in an oven and kept at 180°C for 12 hours. After cooling to room temperature, it was washed with anhydrous ethanol and dried to obtain Cs2NaLuCl6 lead-free double perovskite luminescent material.

[0037] Example 2

[0038] Based on the above embodiment 1, this embodiment provides a Yb 3+ Re 4 A method for preparing a Cs⁻ triple-doped Cs₂NaLuCl₆ lead-free double perovskite luminescent material, wherein the molar ratio of CsCl, NaCl, and LuCl₃•6H₂O is CsCl:NaCl:LuCl₃•6H₂O = 2:1:1, the amount of YbCl₃·6H₂O added is 20% of the amount of LuCl₃·6H₂O, the amount of K₂ReCl₆ added is 1% of the amount of LuCl₃·6H₂O, and the amount of CsF added is 6% of the total amount of Cl⁻. The specific preparation steps are as follows:

[0039] (1) CsCl, NaCl, and LuCl3•6H2O were added to the polytetrafluoroethylene liner according to the proportion to obtain mixture A;

[0040] (2) Next, YbCl3•6H2O, K2ReCl6, CsF and hydrochloric acid are added to mixture A in step (1) and stirred thoroughly to obtain mixture B.

[0041] (3) Finally, the mixture B obtained in step (2) is placed in an oven and kept at 180°C for 12 hours. After cooling to room temperature, it is washed with anhydrous ethanol and dried to obtain Yb³⁺ and Re. 4⁺、F⁻ Triple-doped Cs₂NaLuCl₆ Lead-free Double Perovskite Luminescent Material.

[0042] X-ray diffraction tests were performed on the triple-doped lead-free double perovskite luminescent material obtained in this embodiment and the double-doped lead-free double perovskite luminescent material obtained in Example 1. The test results are as follows: Figure 2 As shown.

[0043] The triple-doped lead-free double perovskite luminescent material obtained in this embodiment was used for SEM observation of its morphology and doping content, such as... Figure 3 As shown.

[0044] The emission spectra of the triple-doped lead-free double perovskite luminescent material obtained in this embodiment and the double-doped lead-free double perovskite luminescent material obtained in Example 1 were measured under 980 nm excitation. The test results are as follows: Figure 4 As shown. By Figure 4 It can be seen that the introduction of F⁻ slightly reduces the emission intensity of the material because F⁻ - The introduction of Yb changed 3+ The local crystal field environment causes a slight decrease in its absorption cross section, or a slight increase in its affinity for Re. 4+ Energy transfer loss between them.

[0045] The triple-doped lead-free double perovskite luminescent material obtained in this embodiment and the double-doped lead-free double perovskite luminescent material obtained in Example 1 were subjected to temperature-dependent emission tests under 980 nm excitation. The test results are as follows: Figure 5 As shown. By Figure 5 It can be seen that the Yb³⁺ and Re obtained in Example 1 4 The emission intensity of the dual-doped material at 423 K is 85.7% of its room-temperature emission intensity, while the Yb³⁺ and Re⁻ materials obtained in this embodiment... 4 The emission intensity of the F⁺ and F⁻ triple-doped material at 423 K is 94.7% of the emission intensity at room temperature, indicating that the incorporation of F⁻ is beneficial to improving the material's resistance to thermal quenching and thermal stability.

[0046] The near-infrared luminescence quantum efficiency of the triple-doped lead-free double perovskite luminescent material obtained in this embodiment and the double-doped lead-free double perovskite luminescent material obtained in Example 1 were further tested under 980 nm excitation. The test results are as follows: Figure 9 and Figure 10 As shown. The results indicate that the 20% Yb³⁺ and 1% Re obtained in Example 1... 4 The near-infrared quantum efficiency of the double-doped lead-free double perovskite material is 94.7%. This embodiment uses 6%F⁻, 20%Yb³⁺, and 1%Re⁻ materials. 4 The near-infrared quantum efficiency of the triple-doped lead-free double perovskite material is 89.8%, with only a slight decrease. This indicates that F⁻ doping improves the thermal stability of the material while maintaining a high near-infrared luminescence quantum efficiency.

[0047] When the triple-doped lead-free double perovskite luminescent material obtained in this embodiment is placed in a 980nm chip package, it emits uniform and stable near-infrared light upon electrical excitation, producing clear imaging contours, such as... Figure 11 As shown, the blood vessels in the human hand are clearly visible, making it suitable for LED-driven near-infrared imaging applications.

[0048] Example 3

[0049] Based on Example 1, this example prepares Yb³⁺ and Re with different Yb³⁺ doping amounts. 4 ⁺A lead-free double-doped Cs₂NaLuCl₆ perovskite luminescent material is prepared, wherein the molar ratio of CsCl, NaCl, and LuCl₃•₆H₂O is 2:1:1, the amount of K₂ReCl₆ added is 1% of the molar amount of LuCl₃•₆H₂O, and the amount of YbCl₃•₆H₂O added is 10%, 15%, 20%, 30%, and 40% of the molar amount of LuCl₃•₆H₂O, respectively. The specific preparation steps are as follows:

[0050] (1) Take 5 groups of CsCl, NaCl, and LuCl3•6H2O according to the proportion and add them to the polytetrafluoroethylene liner to mix, and obtain 5 groups of mixture A;

[0051] (2) Next, add the corresponding amounts of YbCl3•6H2O and K2ReCl6 and an equal amount of hydrochloric acid to the 5 mixtures A in step (1) and stir thoroughly to obtain 5 mixtures B.

[0052] (3) Finally, the five mixtures B obtained in step (2) were placed in an oven and kept at 180°C for 12 hours. After cooling to room temperature, they were washed with anhydrous ethanol and dried to obtain five different Yb groups. 3+ Yb doping level 3+ Re 4+ Lead-free double perovskite luminescent material with dual doping Cs2NaLuCl6.

[0053] The emission spectra of the five groups of lead-free double perovskite luminescent materials obtained in this embodiment were tested under 980 nm excitation. The test results are as follows: Figure 6 As shown. By Figure 6 It can be seen that when the amount of YbCl3•6H2O added is 20% of the amount of LuCl3•6H2O, and the amount of K2ReCl6 added is 1% of the amount of LuCl3•6H2O, the resulting lead-free double perovskite luminescent material has better emission intensity.

[0054] Example 4

[0055] Based on Example 1, this example prepares different Re 4+Yb doping level 3+ Re 4+ A lead-free double-perovskite luminescent material, Cs2NaLuCl6, is prepared in the following manner: the molar ratio of CsCl, NaCl, and LuCl3•6H2O is 2:1:1; the amount of YbCl3•6H2O added is 20% of the molar amount of LuCl3•6H2O; and the amounts of K2ReCl6 added are 0.5%, 0.8%, 1%, 1.5%, and 2% of the molar amount of LuCl3•6H2O, respectively. The specific preparation steps are as follows:

[0056] (1) Take 5 groups of CsCl, NaCl, and LuCl3•6H2O according to the proportion and add them to the polytetrafluoroethylene liner to mix, and obtain 5 groups of mixture A;

[0057] (2) Next, add the corresponding amounts of YbCl3•6H2O and K2ReCl6 and an equal amount of hydrochloric acid to the 5 mixtures A in step (1) and stir thoroughly to obtain 5 mixtures B.

[0058] (3) Finally, the five mixtures B obtained in step (2) were placed in an oven and kept at 180°C for 12 hours. After cooling to room temperature, they were washed with anhydrous ethanol and dried to obtain five different Re groups. 4+ Yb doping level 3+ Re 4+ Lead-free double perovskite luminescent material with dual doping Cs2NaLuCl6.

[0059] The emission spectra of the five groups of lead-free double perovskite luminescent materials obtained in this embodiment were tested under 980 nm excitation. The test results are as follows: Figure 7 As shown. By Figure 7 It can be seen that when the amount of YbCl3•6H2O added is 20% of the amount of LuCl3•6H2O, and the amount of K2ReCl6 added is 1% of the amount of LuCl3•6H2O, the resulting material has better emission intensity.

[0060] Example 5

[0061] Based on the superior Yb in Examples 3 and 4 3+ Re 4+ Doping ratio, different F were prepared in this embodiment. - Yb doping level 3+ Re 4+ F -Triple-doped Cs₂NaLuCl₆ lead-free double perovskite luminescent material. The molar ratio of CsCl, NaCl, and LuCl₃•₆H₂O is 2:1:1. The amount of YbCl₃•₆H₂O added is 20% of the amount of LuCl₃•₆H₂O, the amount of K₂ReCl₆ added is 1% of the amount of LuCl₃•₆H₂O, and the amount of CsF added is Cl₂NaLuCl₆. - The specific preparation steps for the amounts of 3%, 6%, 7%, 8%, and 10% of the total amount of substance are as follows:

[0062] (1) Take 5 groups of CsCl, NaCl, and LuCl3•6H2O according to the proportion and add them to the polytetrafluoroethylene liner to mix, and obtain 5 groups of mixture A;

[0063] (2) Next, add the corresponding amounts of CsF, YbCl3•6H2O and K2ReCl6 and an equal amount of hydrochloric acid to the 5 mixtures A in step (1) and stir thoroughly to obtain 5 mixtures B.

[0064] (3) Finally, the five mixtures B obtained in step (2) were placed in an oven and kept at 180°C for 12 hours. After cooling to room temperature, they were washed with anhydrous ethanol and dried to obtain five different F groups. - Yb doping level 3+ Re 4+ F - Triple-doped Cs2NaLuCl6 lead-free double perovskite luminescent material.

[0065] The emission spectra of the five groups of lead-free double perovskite luminescent materials obtained in this embodiment were tested under 980 nm excitation. The test results are as follows: Figure 8 As shown. By Figure 8 It can be seen that when the amount of YbCl3•6H2O added is 20% of the amount of LuCl3•6H2O, the amount of K2ReCl6 added is 1% of the amount of LuCl3•6H2O, and the amount of CsF added is Cl - When the total amount of substance is 6%, the resulting material has better emission intensity.

Claims

1. A lead-free double perovskite luminescent material, characterized in that, The lead-free double perovskite luminescent material uses Cs2NaLuCl6 as the double perovskite matrix and is doped with Yb. 3+ Re 4+ ,F⁻.

2. A method for preparing the lead-free double perovskite luminescent material as described in claim 1, characterized in that, Includes the following steps: S1: Add CsCl, NaCl, and LuCl3•6H2O to the polytetrafluoroethylene liner and mix to obtain mixture A; S2: Add YbCl3•6H2O, K2ReCl6, CsF and hydrochloric acid to mixture A, stir thoroughly, and mix evenly to obtain mixture B; S3: Place mixture B in an oven for reaction, cool to room temperature, wash and dry with anhydrous ethanol to obtain a near-infrared luminescent lead-free double perovskite luminescent material.

3. The method for preparing the lead-free double perovskite luminescent material according to claim 2, characterized in that, In S1, the molar ratio of CsCl, NaCl, and LuCl3•6H2O is CsCl:NaCl:LuCl3•6H2O = 2:1:

1.

4. The method for preparing the lead-free double perovskite luminescent material according to claim 2, characterized in that, In S2, YbCl3·6H2O and K2ReCl6 serve as the Yb³⁺ source and Re source, respectively. 4 The F⁺ source was added, wherein the amount of YbCl3·6H2O added was 20% of the amount of LuCl3·6H2O, and the amount of K2ReCl6 added was 1% of the amount of LuCl3·6H2O; CsF was added as an F⁻ source, and the amount of CsF added was 6% of the total amount of Cl⁻.

5. The method for preparing the lead-free double perovskite luminescent material according to claim 2, characterized in that, In step S3, the reaction conditions of the mixture B in the oven are 180°C for 12 hours.

6. The application of the lead-free double perovskite luminescent material as described in claim 1, or the lead-free double perovskite luminescent material prepared by the method described in any one of claims 2 to 5, in LED imaging.

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